1. Field of the Invention
The present invention relates to integrated circuit packaging. In particular, the present invention relates to a leadless plastic chip carrier with enhanced moisture-resistance.
2. Discussion of the Related Art
Plastic packages with a die attach pad optimized for increased thermal and electrical performances are described, for example, in co-pending patent application (xe2x80x9cFirst Copending Applicationxe2x80x9d), entitled xe2x80x9cOptimized Pad Lead Frame Designxe2x80x9d by N. McClellan et al., Ser. No. 09/222,579, filed on Dec. 28, 1998. To provide additional background information, the disclosure of the First Copending Application is hereby incorporated by reference in its entirety. Such plastic packages, among numerous other advantages, minimize exposure of the die attach pad to the molding compound, provide better placement of the semiconductor die, and allow the same lead frame to be used with semiconductor dies of varying sizes.
The present invention provides additional advantages in addition to those provided by conventional plastic packages with optimized die attach pads.
According to the present invention, an integrated circuit package for accommodating a semiconductor die is provided including: (1) a conductive lead frame, (2) wire-bonds coupling the semiconductor die to various elements of the lead frame, and (3) a plastic or resin encapsulation for enclosing the bond wires and the semiconductor die. The lead frame includes: (a) a die attach pad for accommodating the semiconductor die, (b) a ring provided adjacent to the die attach pad to provide a ground plane, and (c) leads for external connections.
In one embodiment, the attach pad and the ring are spaced from each other by slots filled by the insulative encapsulation, except at one or more designated metal connection points, where they are connected by tie bars. The ring and the die attach pad lock the molding compound at the slots, so as to prevent delamination from the molding compound that may allow moisture to enter the package. In one embodiment, a solder plating is provided on the exposed surface of the lead frame, so as to allow enhanced external electrical contact (e.g., to a printed circuit board).
In one embodiment, the lead frame includes half-etched tie-bars for suspending the ring. The half-etched tie-bars, which are substantially completely enclosed by the molding compound, provide mechanical support for the die attach pad and the ring.